The present invention relates to a geared motor for activating a functional member of a motor vehicle.
Numerous geared motors of this type are already known in the prior art, which comprise a direct-current electric motor, at the end of which is arranged a reducer casing, in which are arranged means for detecting the speed and direction of rotation of the motor, the said means comprising a coded magnetic wheel associated with the output shaft of the motor and at least two Hall effect cells which are offset relative to one another and the output of which is designed to be connected to signal processing/conditioning means.
Such geared motors are used, for example, for ensuring the activation of electric operated windows, electric operated sliding roofs or the like of motor vehicles.
It is necessary, for various reasons, to know the speed and direction of rotation of this motor, in order to control the functioning of the latter.
Means have therefore been installed in these motors which make it possible to record these parameters using a coded magnetic wheel fastened, for example, to the output shaft of the motor, this coded magnetic wheel being associated with at least two Hall effect cells.
Reference may be made, for example, to the documents U.S. Pat. Nos. 4,857,784, 5,422,551 and 5,500,585 which describe such structures.
However, in all the geared motors of the prior art, the Hall effect cells are arranged opposite the peripheral edge of the coded magnetic wheel and in alignment with the latter.
This arrangement, then, has some disadvantages, particularly in terms of the accuracy required for mounting these Hall effect cells and of the resulting bulk of the geared motor.
In fact, it is known that, in order to function correctly, these Hall effect cells must be arranged with relatively high accuracy in relation to the coded magnetic wheel, so that, in order to obtain such accurate positioning, it is necessary for the manufacture and assembly of the geared motors to be controlled accurately.
Moreover, arranging the Hall effect cells in the extension of the coded magnetic wheel increases the radial bulk of this geared motor.
The object of the invention is, therefore, to solve these problems.
For this purpose, the subject of the invention is a geared motor for activating a functional member of a motor vehicle, of the type comprising a direct-current electric motor, at the end of which is arranged a reducer casing, in which are arranged means for detecting the speed and direction of rotation of the motor, the said means comprising a coded magnetic wheel associated with the output shaft of the motor and at least two Hall effect cells which are offset relative to one another and the output of which is designed to be connected to signal processing/conditioning means, characterized in that the Hall effect cells are placed opposite at least part of a lateral face of the coded wheel between the latter and means for concentrating the magnetic flux.